Bring a large pot of water to the boil over high heat. Make a X in the bottom of each tomato using a small, sharp knife (this is to make it easier to peel the skin off the tomatoes). Have a large bowl of iced water handy. Carefully place the tomatoes into the water in 3 to 4 batches. Leave submerged for 1 minute. Remove with a slotted spoon to the iced water. Let stand in the iced water for 30 seconds. Repeat with the remaining tomatoes. Peel the skin from the tomatoes starting from where you marked the tomatoes; discard the skins and remove the cores. Chop the tomatoes and set aside.

Drain the water from the pot, rinse and dry it ready to use to make the sauce.

Heat the oil in the same pot over medium-high heat. Add the onion and garlic. Cook, stirring occasionally, for 5 to 10 minutes until the onion is softened.

Add the tomato paste, tomato, sugar, vinegar, salt and pepper; stir. Bring the mixture to a boil. Then reduce the heat to medium-low. Cook, uncovered, stirring occasionally, for about 40 minutes or until the sauce is thickened but still liquid.

Spoon into freezer-safe jars or containers, leaving at least 1/2-inch (1.25cm) space for the sauce to expand as it freezes. Makes 6 cups/ 1 1/2 quarts / 1 1/2 liters.